JP2013508195A - Method and apparatus for ejecting droplets having straight trajectories - Google Patents

Abstract

Described herein is a method and apparatus for driving a droplet ejection device to produce droplets having straight droplet trajectories. In one embodiment, a method of driving a droplet ejection device having an actuator includes applying a multi-pulse waveform having at least one drive pulse and a straightening correction pulse to the actuator to cause fluid to flow with at least one drive pulse. Forming droplets. Next, the method includes causing a droplet ejection device to eject a droplet having a straight trajectory in response to a pulse of a multi-pulse waveform. The straightening pulses are designed to ensure that the droplets are ejected without droplet trajectory errors.
[Selection] Figure 4

Description

  Embodiments of the present invention relate to droplet ejection, and more particularly to ejecting droplets having straight trajectories.

  Droplet ejection devices are used for a variety of purposes, most commonly for printing images on a variety of media. These droplet ejection devices are often called ink jets or ink jet printers. Drop-on-demand droplet ejection devices are used in many applications because of their versatility and economy. A drop-on-demand device ejects one or more droplets in response to a specific signal, usually an electrical waveform or waveform, which can include a single pulse or multiple pulses. Different portions of the multi-pulse waveform can be selectively activated to generate droplets. One or more drive pulses form a droplet from a nozzle of the droplet ejection device.

  Typically, a droplet ejection device includes a flow path from a fluid source to a nozzle path. The nozzle path terminates at a nozzle opening where droplets are ejected. For example, the ejection of droplets is controlled by pressurizing the fluid in the flow path using an actuator that can be a piezoelectric deflector, a thermal bubble jet generator, or an electrostatic deflection element. A typical print head has an array of channels with corresponding nozzle openings and associated actuators, and the ejection of droplets from each nozzle opening can be controlled separately. In drop-on-demand printheads, droplets are selectively ejected to specific target pixel locations as each actuator is activated and the printhead and substrate are moved relative to each other.

  The droplet ejection device needs to continuously generate droplets, acquire a required droplet amount, accurately discharge a material, and realize a desired discharge amount. Droplet placement errors with respect to the target degrade the image quality on the target. FIG. 1 shows different types of placement errors. The droplet 120 is ejected through the nozzle plate 110 toward the target 130. Vertical line 170 represents an ideal straight drop trajectory. However, nozzle error 180 occurs due to misalignment of the nozzle with respect to the target. The vertical line 180 represents a straight droplet trajectory from the nozzle to the target, and this line is orthogonal to the nozzle plate 110. The angle theta formed between the vertical line 180 and the actual trajectory 190 of the droplet represents the ejection trajectory error 150. The total droplet placement error is equal to the combination of nozzle placement error and jet trajectory error.

  “Permanent” jet straightness occurs when the jet is always straight or always bent. Permanently bent jets are generally the result of nozzle damage and / or contamination within or around the nozzle. Temporary injection linearity occurs when an injection that is straight after priming becomes bent after the injection period. These injections may or may not self-repair after a further injection period. Injection trajectory errors are due to bent injections. 2 and 3 show examples of bent jets. Region 202 shows an injection bent in the same direction. Region 204 shows twinning where adjacent jets are bent in the opposite direction. FIG. 3 shows the printed area resulting from the curved jet. An arrow 210 indicates a region where the distance between the lines becomes non-uniform due to the bent jet. Arrow 220 points to an area where the position of the printed line has changed over a period of time due to temporary jet linearity. An arrow 230 indicates a region where two adjacent lines are merged into one line by pairing. In any case, the image quality generated by the bent jet is reduced.

  Described herein is a method and apparatus for driving a droplet ejection device to produce droplets having straight droplet trajectories. In one embodiment, a method of driving a droplet ejection device having an actuator includes: applying at least one drive pulse by applying a multi-pulse waveform having at least one drive pulse and a straightening pulse to the actuator. Forming fluid droplets. Next, the method includes causing a droplet ejection device to eject a droplet having a straight trajectory in response to a pulse of a multi-pulse waveform. The straightening pulses are designed to ensure that the droplets are ejected without droplet trajectory errors.

  The invention is illustrated by way of example and not limitation in the figures of the accompanying drawings.

It is sectional drawing of the nozzle plate of the inkjet print head with respect to the target by the conventional method. Fig. 3 shows a droplet ejected by a curved jet according to a conventional technique. FIG. 6 shows a reduced print image resulting from bent jetting, temporary jet linearity, and pairing according to conventional techniques. 1 is an exploded view of a shear mode piezoelectric inkjet printhead, according to one embodiment. FIG. 2 is a side cross-sectional view through an inkjet module, according to one embodiment. FIG. FIG. 3 is a perspective view of an inkjet module showing the position of electrodes relative to a pump chamber and piezoelectric element, according to one embodiment. FIG. 7B is an exploded view of another embodiment of the inkjet module shown in FIG. 7B. 1 shows an inkjet module. FIG. 6 is an exploded view of a shear mode piezoelectric inkjet printhead, according to another embodiment. 1 is a perspective view of an inkjet module showing a cavity plate, according to one embodiment. FIG. FIG. 4 shows a flow diagram of an embodiment for driving a droplet ejection device with a multi-pulse waveform having straight straightening pulses to eject a droplet having a straight trajectory. A single drive pulse 1102 is shown with a tail that is off-center with respect to the retracting meniscus 1104 and the nozzle opening, according to conventional techniques. FIG. 6 shows a single drive pulse and straightening pulse with a raised meniscus and a tail centered at the nozzle opening, according to one embodiment. FIG. 6 illustrates a multi-pulse waveform with one drive pulse and one straightening pulse, according to one embodiment. Fig. 4 shows a multi-pulse waveform according to one embodiment. FIG. 6 illustrates asymmetric wetting around a nozzle, according to one embodiment. Fig. 5 shows a single pulse waveform and corresponding droplet ejection according to conventional techniques. FIG. 6 illustrates a multi-pulse waveform and corresponding droplet ejection, according to one embodiment. FIG. 6 illustrates a single pulse waveform and corresponding drop ejection according to another embodiment. FIG. 6 illustrates a multi-pulse waveform and corresponding droplet ejection, according to one embodiment. FIG. 4 illustrates droplet ejection at different temperatures and ink viscosity levels according to some embodiments. FIG.

  Described herein is a method and apparatus for driving a droplet ejection device to produce droplets that are ejected to have a straight trajectory. In one embodiment, a method of driving a droplet ejection device having an actuator includes applying a multi-pulse waveform having at least one drive pulse and a straightening correction pulse to the actuator, thereby causing fluid fluid to flow with at least one drive pulse. Forming drops. Next, the method includes causing a droplet ejection device to eject a droplet having a straight trajectory in response to a pulse of a multi-pulse waveform. The straightening pulses are designed to ensure that the droplets are ejected without droplet trajectory errors.

  Straightening pulses provide a straightening of the droplets formed by at least one drive pulse by raising the meniscus position of the fluid beyond the nozzle, reducing potential droplet trajectory errors. Straightening pulses also reduce asymmetric wetting problems by changing the meniscus characteristics. In some embodiments, the droplet ejection device ejects additional fluid round masses in response to pulses of a multi-pulse waveform or in response to pulses of an additional multi-pulse waveform.

  FIG. 4 is an exploded view of a shear mode piezoelectric inkjet printhead, according to one embodiment. Referring to FIG. 4, the piezoelectric inkjet head 2 includes a plurality of modules 4 and 6 assembled to a collar element 10, to which a manifold plate 12 and an orifice plate 14 are attached. The piezoelectric inkjet head 2 is an example of various types of print heads. According to one embodiment, ink is introduced through a collar 10 into a jet module operated by a multi-pulse waveform and ejects ink droplets of various droplet sizes from orifices 16 on an orifice plate 14. . Each of the inkjet modules 4 and 6 includes a body 20 formed of a thin rectangular block of material such as sintered carbon or ceramic. In both sides of the body, a series of wells 22 are machined that form the ink pump chamber. Ink is introduced through an ink fill path 26 which is also machined into the body.

  Opposing surfaces of the body are covered with flexible polymer films 30 and 30 'that include a series of electrical contacts arranged to be located above the pump chamber in the body. The electrical contacts are connected to leads, which can then be connected to flexible printed circuit boards 32 and 32 'including driver integrated circuits 33 and 33'. Films 30 and 30 'can be flexible printed circuit boards. Each flexible printed circuit board film is sealed to the body 20 by a thin epoxy layer. The epoxy layer is thin enough to fill the surface roughness of the jet body and provide a mechanical bond, but also thin enough that only a small amount of epoxy is squeezed from the bond line into the pump chamber.

  Each of the piezoelectric elements 34 and 34 ', which can be a single monolithic piezoelectric transducer (PZT) member, is disposed on the flexible printed circuit boards 30 and 30'. Each of the piezoelectric elements 34 and 34 'has an electrode formed by removing a conductive metal vacuum-deposited on the surface of the piezoelectric element by chemical etching. The electrode on the piezoelectric element is in a position corresponding to the pump chamber. The electrodes on the piezoelectric element are in electrical engagement with corresponding contacts on the flexible printed boards 30 and 30 '. As a result, electrical contact is made to each side of the piezoelectric element where action is to be effected. The piezoelectric element is fixed to the flexible printed circuit board by a thin epoxy layer.

  FIG. 5 is a cross-sectional side view through an inkjet module, according to one embodiment. Referring to FIG. 5, the piezoelectric elements 34 and 34 ′ are sized to cover only a portion of the body including the machined ink pump chamber 22. The main body portion including the ink filling path 26 is not covered with the piezoelectric element.

  The ink filling path 26 is sealed by flexible printed circuit board portions 31 and 31 'attached to the outer portion of the module body. The flexible printed circuit board forms (and seals) a soft cover over the ink fill path, approximating the free surface of the fluid exposed to the atmosphere.

  During normal operation, the piezoelectric element first operates to increase the capacity of the pump chamber, and then after a period of time, the piezoelectric element is deactivated and returns to its original position. By increasing the capacity of the pump chamber, a negative pressure wave is generated. This negative pressure begins in the pump chamber and travels toward the ends of the pump chamber (in the direction of the orifice and ink fill path as suggested by arrows 33 and 33 '). When the negative pressure wave reaches the end of the pump chamber and encounters a large area of the ink filling path (which communicates with the approximate free surface), the negative pressure wave reflects back to the pump chamber as a positive pressure wave and returns to the orifice It is transmitted towards. A positive pressure wave is also generated when the piezoelectric element returns to its original position. The timing of stopping the operation of the piezoelectric element is when the positive pressure wave and the reflected positive pressure wave are added when reaching the orifice.

  FIG. 6 is a perspective view of an inkjet module showing the position of the electrodes relative to the pump chamber and piezoelectric element, according to one embodiment. Referring to FIG. 6, an electrode pattern 50 on a flexible printed circuit board 30 for the pump chamber and piezoelectric elements is shown. The piezoelectric element has an electrode 40 that contacts the flexible printed circuit board on the side of the piezoelectric element 34. Each electrode 40 is arranged and sized to correspond to a pump chamber 45 in the jet body. Each electrode 40 substantially corresponds to that of the pump chamber, but has an elongated region 42 having a length and width that is shorter and narrower, so that the perimeter of the electrode 40 and the sides and ends of the pump chamber. There is a gap 43 between them. These electrode regions 42 located centrally on the pump chamber are drive electrodes. The comb-shaped second electrode 52 on the piezoelectric element typically corresponds to a region outside the pump chamber. This electrode 52 is a common (ground) electrode.

  The flexible printed circuit board has an electrode 50 in contact with the piezoelectric element on the side 51 of the flexible printed circuit board. The electrodes of the flexible printed circuit board and the piezoelectric element overlap sufficiently so that the flexible printed circuit board and the piezoelectric element are in good electrical contact and are easily aligned. The flexible printed circuit board electrode extends beyond the piezoelectric element (in the vertical direction in FIG. 6) and allows connection (eg, soldering or non-conductive paste) to the flexible printed circuit board 32 that includes the drive circuitry. To do. There is no need to have two flexible printed circuit boards 30 and 32. A single flexible printed circuit board can also be used.

  FIG. 7A is an exploded view of another embodiment of the inkjet module shown in FIG. 7B. In the present embodiment, the injection nozzle body is composed of a plurality of parts. The frame of the ejection port body 80 is sintered carbon and includes an ink filling path. Mounted on each side of the jet body are reinforcing plates 82 and 82 ', which are thin metal plates designed to strengthen the assembly. Mounted on the stiffener plate are cavity plates 84 and 84 ', which are thin metal plates in which the pump chamber is chemically milled. Flexible printed circuit boards 30 and 30 'are attached to the cavity plate, and piezoelectric elements 34 and 34' are attached to the flexible printed circuit board. All of these elements are joined together by epoxy. The flexible printed circuit boards 32 and 32 'including the drive circuit are attached by a soldering process.

  FIG. 8 is a shear mode piezoelectric inkjet printhead according to another embodiment. The ink jet print head shown in FIG. 8 is similar to the print head shown in FIG. However, the printhead of FIG. 8 has a single inkjet module 210 as opposed to the two inkjet modules 4 and 6 of FIG. In some embodiments, the inkjet module 210 includes the following components: carbon body 220, reinforcing plate 250, cavity plate 240, flexible printed circuit board 230, PZT member 234, nozzle plate 260, ink filling. Includes path 270, flexible printed circuit board 232, and drive electronics 233. These components have functions similar to those described above in connection with FIGS.

  According to one embodiment, the cavity plate is shown in more detail in FIG. The cavity plate 240 includes a hole 290, an ink fill path 270, and a pump chamber 280 that is deformed or actuated by PZT. As shown in FIGS. 8 and 9, an inkjet module 210, which can be referred to as a droplet ejection device, includes a pump chamber. The PZT member 234 (eg, actuator) operates to change the pressure of the fluid in the pump chamber in response to drive pulses applied to the drive electronics 233. In one embodiment, the PZT member 234 ejects a fluid droplet from the pump chamber. The driving electronic device 233 is connected to the PZT member 234. During operation of the inkjet module 210, the drive electronics 233 drives the PZT member 234 with a multi-pulse waveform having at least one drive pulse and at least one straightening pulse. At least one drive pulse forms a fluid droplet. The straightening pulse corrects the potential droplet trajectory error of the droplet. The driving electronics causes the actuator to eject a droplet having a straight trajectory in response to a pulse having a multi-pulse waveform. In one embodiment, the multi-pulse waveform can include a first drive pulse, a second drive pulse having a first peak voltage, followed by a straightening pulse having a second peak voltage. . The second peak voltage can be based on the first peak voltage.

  FIG. 10 shows a flow diagram of a process for driving a droplet ejection device with a multi-pulse waveform to eject a droplet having a straight trajectory, according to one embodiment. The process of driving a droplet ejection device having an actuator comprises: at processing block 1002, applying a multi-pulse waveform having at least one drive pulse and a straightening correction pulse to the actuator to cause a fluid droplet with at least one drive pulse. Forming. Next, the process includes raising the meniscus position of the fluid in the nozzle beyond the nozzle at process block 1004. Next, the process includes causing the droplet ejection device to eject a droplet having a straight trajectory in response to a pulse of the multi-pulse waveform at process block 1006. Straightening pulses are designed to eject droplets without droplet trajectory errors. Since the jet velocity response, which is characterized by the droplet ejection speed of the droplet ejection device, is almost zero in the straightening pulse, the straightening pulse does not form a sub-drop or satellite. Also designed to inject. Straightening pulses provide straightening of the droplets formed by at least one drive pulse and reduce potential droplet trajectory errors.

  In some embodiments, the nozzle has a non-circular shape. At least one drive pulse is adjusted to approximately the maximum droplet velocity in the frequency response of the droplet ejector to form a droplet, and the linear correction pulse causes the droplet to drop with reduced droplet trajectory error. In order to fire, it is adjusted to a nearly minimal drop velocity in the frequency response of the drop ejector. The multi-pulse waveform includes a drive pulse having a first peak voltage, followed by a straightening pulse having a second peak voltage, the second peak voltage being based on the first peak voltage. In one embodiment, the second peak voltage is less than the first peak voltage. By increasing the second peak voltage, the meniscus position of the fluid in the nozzle rises further beyond the nozzle.

  In one embodiment, the droplet ejection device ejects additional fluid round masses in response to pulses of a multi-pulse waveform or in response to pulses of an additional multi-pulse waveform. The waveform can include a series of sections connected to each other. Each interval may include a specific number of samples including a certain period (eg, from 1 microsecond to 3 microseconds) and an associated amount of data. The sample period is long enough for the drive electronics control logic to enable or disable each spray nozzle during the next waveform interval. The waveform data is stored in a table as a series of address, voltage and flag bit samples and can be accessed by software. The waveform provides the data necessary to generate a single size droplet and a variety of different size droplets.

  As described above, temporary injection linearity occurs when an injection that is straight immediately after priming becomes bent after the injection period. These injections may or may not self-repair after a further injection period. Injection trajectory errors are due to bent injections. Print heads with non-circular nozzles (eg, square nozzles with sharp or rounded edges) are more prone to trajectory errors. This phenomenon can be affected by the meniscus position of the fluid. When the drop tails separate, if the meniscus is located near the face of the nozzle, the tail can adhere to the sides / corners of the nozzle, resulting in drop trajectory errors. When the tail is separated, when the meniscus rises from the nozzle or in some cases retracts (retracts), the tail is located in the center of the raised ink mass at the nozzle and the jet is straight .

  In one embodiment, a straightening pulse is used to cause the meniscus to rise from the nozzle so that the amplitude of the straightening pulse is lower than the drive pulse and subsequent drive pulses. In some jetting designs, and under certain conditions regarding meniscus pressure, viscosity, and ink sound speed, the meniscus position rises during tail separation without additional pulses on the waveform.

  FIG. 11A shows a single drive pulse 1102 that creates a retracting meniscus 1104 and moves the tail 1106 to one side of the nozzle opening 1108. FIG. 11B shows a single drive pulse 1120 and a straightening pulse 1130 that produces a raised meniscus 1134 and centers the tail 1136 relative to the nozzle opening 1140. Alternatively, straightening pulses can be added to the drive pulse sequence to eject droplets with straight trajectories. In order to minimize droplet trajectory errors, it is desirable that the droplet tail be centered with respect to the nozzle opening. This improves image quality and product quality. Increasing temperature can change the meniscus characteristics, which can allow for a more favorable symmetrical wetting of the spray nozzle. The straightening pulse further changes the meniscus bounce and provides a better wetting.

  FIG. 12 shows a multi-pulse waveform with one drive pulse and one straightening pulse, according to one embodiment. In operation, each inkjet can eject a single droplet in response to a multi-pulse waveform. An example of a multi-pulse waveform is shown in FIG. In this example, the multi-pulse waveform 1200 has two pulses. Each multi-pulse waveform is typically separated from subsequent waveforms by a period corresponding to an integer multiple of the injection period (ie, a period corresponding to the injection frequency). Each pulse is characterized as having a “fill” ramp corresponding to an increase in pump element volume and a “fire” ramp (slope opposite to the fill ramp) corresponding to a decrease in pump element volume. Can do. Typically, expansion and contraction of the pump element volume results in pressure fluctuations within the pump chamber, thereby driving fluid out of the nozzle.

  In certain embodiments, the multi-pulse waveform 1200 has a drive pulse 1210 that is fired to cause a droplet ejection device to eject a droplet of fluid. In one embodiment, drive pulse 1210 has a voltage level between 0 and 256 corresponding to a predetermined voltage range, depending on the particular drop ejection application. In one embodiment, the drive pulse 1210 has a peak voltage V1 of about 256 volts. The straightening correction pulse 1220 has a peak voltage V2 based on the peak voltage of the drive pulse 1210.

  In some embodiments, the peak voltage V1 of the straightening correction pulse 1220 is less than the peak voltage V2 of the drive pulse 1210. In one embodiment, V2 is 25% of V1. V2 is determined by the ink viscosity. The lower the ink viscosity, the lower the V2 value required. V2 needs to be large enough to reduce droplet trajectory errors and to straighten the jet. A larger V2 increases the meniscus bulge during droplet separation.

  The first time period t 1 is associated with the first delay segment 1212, the fill segment 1214, and the second delay segment 1216 of the drive pulse 1210. The second time period t2 is associated with a drive pulse firing segment 1218 and a third delay segment 1219. The third period t3 is associated with the fill segment 1222 and the fourth delay segment 1224 of the drive pulse 1220. In high frequency operation, it is desirable to minimize t2 and further reduce or eliminate droplet trajectory errors with pulses 1220. In one embodiment, t2 is at least 63% of t1. In another embodiment, t2 is about 80% of t1, and t3 is about 55% of t1. For high frequency operation, the third period t3 needs to be minimized and no further separate droplets or subdroplets need to be generated. For low frequency operation, the second and third periods can be longer.

  In the multi-pulse waveform 1200, the driving pulse is generated before one straightening correction pulse. In other embodiments, additional drive pulses occur before one or more straightening pulses. The droplet can have a native droplet size associated with the droplet ejection device. In one embodiment, the waveform 1200 produces 25-35 ng drops from an ejector that produces nominally 25-35 ng drops for a particular printhead and ink type. In another embodiment, the waveform 1200 produces 7-10 ng drops from an ejector that produces a nominal 7-10 ng drop for a particular printhead and ink type.

  In certain embodiments, other waveform configurations can be considered. In one embodiment, more than two drive pulses can be used to generate a droplet. In some applications, one or more drive pulses may be negative, or the linear correction pulse may be negative.

  FIG. 13 illustrates a multi-pulse waveform according to one embodiment. Sections 1-4 correspond to pulses 1320, 1330, 1340, 1350, respectively. These pulses can produce a variety of droplet sizes. For example, natural small droplet sizes can be generated in intervals 3 and 4 corresponding to pulses 1340 and 1350. Intermediate droplet sizes can be generated in intervals 2 and 3 corresponding to pulses 1330 and 1340. Large droplet sizes can be generated in intervals 1 and 2 corresponding to pulses 1320 and 1330. A pulse 1350 or another straightening pulse can be added to either of the drive pulses, if necessary, to eject a droplet having a straight trajectory.

  In one embodiment, one or more drive pulses are adjusted to approximately the maximum droplet velocity in the frequency response of the droplet ejector. This is necessary to keep the entire waveform time short and is a requirement for high frequency operation.

  The straightening pulse is adjusted to approximately the minimum droplet velocity in the frequency response of the droplet ejector. At this frequency, the jet velocity response, characterized by the droplet velocity, is approximately zero. For this reason, the straightening correction pulse does not eject sub-droplets or satellite droplets.

  FIG. 14 illustrates the formation of asymmetric wetting around the nozzle, according to one embodiment. Asymmetric wetting around the nozzle over a period of time is a potential cause of temporary jet linearity. For example, the image associated with time period t0-t5 shows a sequence of time with asymmetric wetting problems. The time interval between successive images is from 1 second to 3 seconds. The straightening pulse that occurs after the drive pulse reduces asymmetric wetting and reduces the problem of temporary jet linearity.

  FIG. 15 shows a single pulse waveform and corresponding drop ejection according to a conventional approach. The drive pulse 1610 has a pulse width of 7.168 microseconds, a peak voltage of about 60 volts, and a frequency of 8.2 kHz. A droplet is ejected from the nozzle opening, which is indicated by a 5 microsecond time slice at time slice 1650. The droplets at the time of separation are offset from the center with respect to the nozzle opening and have a droplet trajectory error. The meniscus position at the time of separation is retracted into the nozzle opening.

  FIG. 16 illustrates a multi-pulse waveform and corresponding droplet ejection, according to one embodiment. The drive pulse 1710 has a pulse width of 7.168 microseconds, a peak voltage of about 60 volts, and a frequency of 8.2 kHz. The subsequent straightening pulse 1720 has a similar peak voltage and a pulse width that is half that of the pulse 1720. A droplet is ejected from the nozzle opening, which is indicated by a 5 microsecond time slice at time slice 1750. The droplet at the time of separation is centered with respect to the nozzle opening, and the droplet trajectory error is reduced. The meniscus position at the time of separation protrudes beyond the nozzle opening.

  FIG. 17 shows a single pulse waveform and corresponding drop ejection according to another conventional approach. The drive pulse 1810 has a peak voltage of about 250 volts and a frequency of 1 kHz. The droplets at the time of separation are shifted from the center with respect to the nozzle opening, and the meniscus position at the time of separation is set back in the nozzle opening.

  FIG. 18 illustrates a multi-pulse waveform and corresponding droplet ejection, according to one embodiment. The drive pulse 1910 has a peak voltage of about 250 volts and a frequency of 1 kHz. Subsequent straightening pulses 1920 have substantially lower peak voltages and shorter pulse widths. The droplet at the time of separation is centered with respect to the nozzle opening, and the droplet trajectory error is reduced. The meniscus position at the time of separation protrudes beyond the nozzle opening.

  FIG. 19 illustrates droplet ejection for different temperatures and ink viscosity levels according to some embodiments. Increasing temperature reduces ink viscosity, which results in more favorable meniscus properties and symmetrical wetting. Droplet ejection images associated with high temperatures (eg, 45 degrees Celsius, 55.5 degrees Celsius) and lower ink viscosities (eg, 6.5 cP, 4.9 cP) show straight drop ejection.

  However, lower ink viscosities can lead to other problems, such as UV ink instability, solvent drying rates, and reduced meniscus decay that causes air gulp. A straightening pulse can be used with one or more drive pulses to eject a droplet having a straight trajectory to a target. Straightening pulses can be used with various temperature ranges and ink viscosities to avoid problems associated with lower ink viscosities. This improves image quality and product quality in printing applications.

  It should be understood that the above description is illustrative rather than limiting. Many other embodiments will be apparent to those of skill in the art upon reading and understanding the above description. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

2: Piezoelectric inkjet heads 4, 6, 210: Inkjet module 10: Color element 12: Manifold plate 14: Orifice plate 16: Orifice 20: Main body 22, 45: Pump chamber 26, 270: Ink filling paths 30, 30 ', 32, 32' 230, 232: Flexible printed circuit boards 34, 34 ': Piezoelectric elements 40, 52: Electrodes 42, 202, 204: Area 43: Gap 45, 280: Pump chamber 50: Electrode pattern 80: Injection port bodies 82, 82 ', 250: Reinforcing plates 84, 84', 240: Cavity plate 110, 260: Nozzle plate 120: Droplet 130: Target 140: Nozzle placement error 150: Injection trajectory error 160: Droplet placement error 170: Vertical line 180: Nozzle error 190: Actual track 220: Carbon body 233: Drive electronic machine 234: PZT member 1102: single drive pulse 1104: backward meniscus 1106, 1136: tail 1108, 1140: nozzle opening 1130, 1220, 1720, 1920: straightening correction pulse 1134: raised meniscus 1200: multipulse waveform 1210, 1218, 1610, 1710, 1810, 1910: drive pulse 1212: first delay segment 1214, 1222: filling segment 1216: second delay segment 1219: third delay segment 1224: fourth delay segment 1320, 1330, 1340, 1350: Pulse 1650, 1750: Time slice

Claims (20)

A method for driving a droplet ejection device having an actuator and a nozzle, comprising:
Forming a fluid droplet with the at least one drive pulse by applying to the actuator a multi-pulse waveform having at least one drive pulse and a straightening pulse following the at least one drive pulse;
In response to the pulses of the multi-pulse waveform, causing the droplet ejection device to eject the droplet having a straight trajectory;
A method comprising the steps of:   The method of claim 1, wherein the nozzle has a non-circular shape.   The method of claim 1, wherein the straightening pulse is designed to ensure that the droplet is ejected without a droplet trajectory error.   4. The method of claim 3, further comprising raising a meniscus position of fluid in the nozzle beyond the nozzle in response to the straightening pulse.   The multi-pulse waveform includes a drive pulse having a first peak voltage and a linear correction pulse having a second peak voltage followed by the second peak voltage, the second peak voltage being equal to the first peak voltage. 5. The method according to claim 4, characterized in that it is based.   The method of claim 5, wherein the second peak voltage is less than the first peak voltage.   6. The method of claim 5, wherein increasing the second peak voltage further raises the meniscus position of the fluid in the nozzle beyond the nozzle.   A first period is associated with the first delay segment, the fill segment, and the second delay segment of the drive pulse, and a second period is associated with the firing segment and the third delay segment of the drive pulse. The method of claim 1, wherein the second period is at least 63% of the first period.   9. The method of claim 8, wherein the second period is about 80% of the first period. A pump chamber;
An actuator coupled to the pump chamber for ejecting fluid droplets from the pump chamber;
Drive electronics coupled to the actuator;
And in operation, the drive electronics causes the actuator to eject the droplet having a straight trajectory formed at a nozzle with at least one drive pulse for forming a droplet of fluid. The actuator is driven by a multi-pulse waveform having a linear correction pulse.   The apparatus of claim 10, wherein the nozzle comprises a non-circular shape.   11. The apparatus of claim 10, wherein the straightening pulse is designed to ensure that the droplet is ejected without a droplet trajectory error.   The apparatus of claim 10, wherein the drive electronics raises the meniscus position of the fluid in the nozzle beyond the nozzle in response to the straightening pulse.   The multi-pulse waveform includes a drive pulse having a first peak voltage and a linear correction pulse having a second peak voltage followed by the second peak voltage, the second peak voltage being equal to the first peak voltage. Device according to claim 10, characterized in that it is based.   The apparatus of claim 14, wherein the second peak voltage is less than the second peak voltage.   A first period is associated with the first delay segment, the fill segment, and the second delay segment of the drive pulse, and a second period is associated with the firing segment and the third delay segment of the drive pulse. 2. The apparatus of claim 1, wherein the second period is at least 63% of the first period. A pump chamber;
An actuator coupled to the pump chamber for ejecting fluid droplets from the pump chamber;
Drive electronics coupled to the actuator;
In operation, the drive electronics includes the liquid having at least one drive pulse for forming a fluid droplet and a straight trajectory formed at the actuator at a nozzle. A print head, wherein the actuator is driven by a multi-pulse waveform having a straightening correction pulse for ejecting a droplet.   18. The printhead of claim 17, wherein the straightening pulse is designed to ensure that the droplet is ejected without a droplet trajectory error.   The multi-pulse waveform includes a drive pulse having a first peak voltage and a linear correction pulse having a second peak voltage followed by the second peak voltage, the second peak voltage being equal to the first peak voltage. 18. A print head according to claim 17, characterized in that it is based.   The inkjet module further includes a carbon body, a reinforcing plate, a cavity plate, a first flexible printed circuit board, a nozzle plate, an ink filling path, and a second flexible printed circuit board. Item 18. The print head according to Item 17.